This invention relates to circuits for fast charging rechargeable batteries, and to DC power supplies utilizing a rechargeable battery.
A network which is capable of fast charging a battery normally employs a rather large, expensive heavy transformer for stepping down the AC line voltage. The sheer size and weight and/or cost of the transformer restricts the number of applications in which fast charging methods are attractive for use in portable battery-powered devices.
In the power tool and lawn tool fields, for instance, the advantage of portability which cordless tools offer is recognized. On the other hand, AC power tools offer essentially continuous operation with uniform power output. The need exists to combine the advantages of each of these systems; the present invention meets this objective with a circuit network which can be used solely as a transformerless battery charging circuit, or which will charge a battery and keep its voltage at the proper level while simultaneously supplying DC power to a load, such as a DC motor.